The name “feta” is registered as a protected designation of origin (PDO) to indicate the salted white cheese traditionally produced in Greece and in particular made with milk originating exclusively from the regions of Macedonia, Thrace, Sterea Ellada (Central Greece), the Peloponnese and the prefecture of Lesbos. The milk used for the production of feta should be—sheep's milk or a mixture of sheep's milk and goats' milk. The milk's origin constitute a basic characteristic of the cheese produced, as it provides it with its organoleptic features—its flavour, aroma, colour and even structure and texture.
As far as their structure is concerned, cooked and smoked meat preparations constitute an “emulsion” with the following constituent components: milk proteins, water (from the meat and milk added) and added fat (fat tissue).
The solidness of the “emulsion” depends basically, inter alia, on the capacity of the meat to retain the water and homogenise the added fat.
More particularly, the muscle proteins and especially the salt-soluble ones (actin, myosin and actomyosin), which represent the largest part (around 60%) of the myofibrils, contribute to the solidness of the “emulsion”, as well as to its succulence. They also act as a protective envelop of the incorporated fat, which constitutes the discontinuous phase of the emulsion and the primary destabilisation factor.
Many products on the international market, which have been accepted by the large majority of consumers, are based on the addition of milk products to meat-based products. Hard cheese (with a short or long maturity time) is primarily used for such products.
According to studies, it has been found that the fatty acid content differs in each kind of cheese and depends on the initial quality of the milk added, on the kind of milk (sheep's milk, cow's milk, goat's milk etc or the percentage of each kind that is added to the milk mixture), the maturation time and the preparation method. Moreover, it also depends on the geographical origin of the milk since local changes in the feedstuffs and in the type of animal diet followed affects the fatty acid content of the milk added to produce the cheese.
The flavour and the aroma, which characterise a certain kind of cheese, results from its maturity, that is the primary decomposition of lactose, fat and protein of the cheese and the secondary conversion of its products, through various fermentation procedures which they undergo during the maturation process of the cheese.
The distinctive flavour and the aroma of each kind of cheese does not result from a specific substance, but from a large number of substances, each one having different taste, but all together and relatively proportionately giving flavour to the cheese and in fact the final flavour which determines which kind of cheese it is. Moreover, from the fatty acids, it is acetic acid which gives an acidic flavour; and rancid butter and caproic, caprylic and capric acids which give a peppery flavour.
Feta is a semi-salted cheese with high acidity. Among the fatty acids contained in the product, acetic acid prevails, but when preparations made from ‘the stomach of a sheep and a goat are included in the volatile enzymes used to coagulate the milk, then, fatty acids C6-C10 strongly contribute to the cheese's flavour, by adding a peppery flavour. Typical feta made with sheep's milk has high ethanol, propanol and butanol content.
The structure of the cheese is a dense mesh of protein fibres differently cross-linked. The fat globules and whey are included in that mesh, that is the humidity and the water-soluble components of the cheese. Over the course of time, during the maturation process of the cheese, many protein fibre links break, releasing calcium and forming soft monocalcium paracaseinate and paracaseinate. The cheese undergoes an internal conversion and obtains its final structure and texture that can be characterised as soft, friable, granular etc.
Every kind of cheese is characterised by the proportion of amino acids, sulphide compounds, acid esters and fatty acids, which result from the proteolysis of the protein mesh.
The uniqueness of feta type cheese products, which have been protected by the Council of the European Union, and which as a cheese has been accepted by a large majority of consumers as a tasty product rich in nutrients, was the reason why we conducted this study.
Nevertheless, the incorporation of oil, compared to the ordinary addition of pork fat, if attempted using classic techniques, gives rises to stability difficulties or the development of destabilizing tensions affecting not only the meat pulp emulsion, but also the final product, which displays the phenomenon of oil exudation.
There are also some established techniques of direct incorporation of vegetable fat, which include the procedure of preliminary heat treatment of oil at 100° C. two consecutive times.
Moreover, olive oil is a more particular case, as its role in human nutrition is discernible among seed oils and other vegetable oils and as it is also internationally acknowledged for the beneficial characteristics of its natural components (see Omega fatty acids and their protective role, low cholesterol levels, polyphenols and their role).